The Guide Stopper is the "L" shaped piece on the trigger system (backwards "L" in the image). Make sure that is pushed all the way in or else you'll get that "slam firing" issue.
If that doesn't work, then the sears are probably broken. Especially with those clones, the sears are too weak for the stock spring.
I still consider myself a newbie with bolt actions, so anyone with real experience can feel free to step in.
Hopefully this makes sense and I wish I knew enough French to make things easier for you
